The invention relates to an elongate vacuum system for coating one or both sides of a flat substrate which can be moved through the vacuum system in a transportation plane by means of a transport system. The vacuum system comprises at least one magnetron provided with magnetron surrounding area and is subdivided into successive compartments in the direction of transportation of the substrate by closeable separating walls comprising suction openings, which can be evacuated either directly via a vacuum connection located on the compartment or indirectly via a suction opening in the separating wall. At least one compartment comprises an upper partial compartment which is located above the substrate, the said partial compartment comprising, in at least one of the outer walls thereof, a closeable upper opening.
A coating system which enables coating on both sides of a flat substrate during a single conveyance of the substrate through the system is described in EP 1 179 516 A1. The simultaneous arrangement of targets above and below the substrate moved through the system by means of a transport system enables simultaneous coating on both substrate surfaces within this section. At the same time, although the coating space is subdivided into several sections by barriers projecting into this, the coating process can nevertheless only be operated in the sections with the same or similar sputter atmosphere.
For the simultaneous operation of a coating system with process atmospheres deviating from one another considerably, the subdivision of the coating system into several sections to be evacuated separately as well the separation into coating and evacuation sections is universally known. Such a coating system is outlined in the European patent EP 783 174. It is essentially characterized by a large number of sections located next to one another in the direction of substrate transportation, which together form a vacuum chamber and are connected to one another via a passage, which forms the transportation plane for the flat substrate. Usually, adjoining coating sections each exhibiting a cathode are separated by at least one section capable of evacuation. The side separating walls between the evacuation and coating sections comprise suction openings via which the adjoining coating sections are evacuated indirectly by a connected vacuum pump.
When separating two adjoining coating sections by only one evacuation section, the vacuum pump located there consequently evacuates the, viewed in regard to the direction of transportation, previous and subsequent coating section. As a result of this, two gas flows. In opposite directions encounter each other in the evacuation section, which leads to turbulence and has a deleterious effect on the evacuation process and the performance values of the vacuum pump.
If the various coating sections are operated with different sputter atmospheres, further sections connected to the vacuum pump are necessary beside the evacuation section, which serve as pressure stages or for the gas separation. In this case, the coating system is elongated by the additionally required section, which leads to very longitudinally extended systems with large evacuation volumes when locating next to one another several different sputter atmospheres, sputter powers and/or cathode materials.
In a further development of the system, which is described in the patent specification DE 197 33 940, the evacuation sections are shortened in comparison to the coating sections and separated in the center by a transverse bulkhead arranged transverse to the direction of transportation, so that the vacuum pumps located in a series above the transverse bulkhead evacuate either the previous or the subsequent coating section by means of suitable recesses in the transverse bulkhead and corresponding to positioned baffle plates, depending on the adjustment of the baffle plate. This asymmetrical (as alternate) allocation of the pumps through the adjustment of the baffle plate leads to a pressure gradient and hence to deviations in the sputter conditions within the adjoining, indirectly evacuated coating section.
In this arrangement as well, a coating section usually follows an evacuation section, whereby both sections exhibit different dimensions. Correspondingly, an opening with different dimensions for each section type is incorporated in the upper wall of each section, which holds either a vacuum pump or a cover. A cathode removal with each cover including its cathode surroundings, comprising screens and media feed and extraction, can be mounted on each cover. At the same time, it proves to be very advantageous that the sequence of the sections cannot be changed on account of their different sizes for each coating system.
The cathode and its cathode environment is omitted in at least one coating section which is located between the coating sections to be separated and their adjoining evacuation sections in order to realize a gas separation for operating the system with different sputter conditions. In addition to this, the baffle plates are placed in the adjoining evacuation sections in such a way that both pumps evacuate the separation section located between this. As a result of this, and because, as described, only every second one of the next pumps series but one evacuates the coating sections coming before or after the gas separation, the pump power is significantly reduced in the coating sections located next to the gas separation, which leads to deviations in the sputter conditions between the sections.